The problem with most portraits that folk download from NWN Vault is that no consistant naming conventions are used. I've long, long considered making a decent mega pack from my own Portrait folder but just haven't had the time. It'd be nice to have only male dwarf pics appear when I make one and female halflings when thats chosen, etc... .
A big problem would be getting folks to adapt it though. Most PWs would need to create an NPC or Convo so a PC could change their portraits to match the hak/override used. Even then, most players wouldn't care if it doesn't affect what they see on their own screens.
Even when a specific PW has a portrait pack they endorse, I've found that more often than not, parts of one PW's pack override anothers.